1. Field of the Invention
The present invention relates to a capacitor, a method for producing the same and method for producing a dielectric body. Particularly, this invention relates to a capacitor wherein a dielectric body formed of a basic dielectric substance mixed with conductive substance is interposed between a pair of electrodes, a method for producing the same and a method for producing a dielectric body obtained by mixing conductive substance in a basic dielectric substance.
2. Description of the Related Art
A capacitance of a capacitor is given by the following formula: EQU C=(.epsilon..sub.0) (.epsilon..sub.1) (S/d)
wherein C: capacitance of capacitor
.epsilon..sub.0 : relative dielectric constant in vacuum PA1 .epsilon..sub.1 : relative dielectric constant of dielectric body PA1 S: area of dielectric body PA1 d: thickness of dielectric body PA1 after a conductive body has been formed by mixing the conductive substance with the dielectric substance, providing a pair of electrodes while interposing the conductive body therebetween, and PA1 intermittently applying an electric current or voltage to the electrodes, high enough to electrically break conductive paths formed in the conductive body by the conductive substance, so that the conductive body is converted to the dielectric body. PA1 after a conductive body has been formed by mixing the conductive substance with the dielectric substance, interposing the conductive body between a pair of electrodes, and PA1 intermittently applying an electric current or voltage to the electrodes, high enough to electrically break conductive paths formed in the conductive body by the conductive substance, so that the conductive body is converted to the dielectric body.
To increase the capacitance (C) of the capacitor, it is necessary to enlarge the area (S) of the dielectric body or reduce the thickness (d) of the dielectric body.
In Japanese Unexamined Patent Publication (Kokai) No. 3-87091, a method for producing an alumina ceramic circuit board is proposed wherein a green sheet formed of aluminum powder as a ceramic material added with molybdenum powder and/or tungsten powder in a range between 5 and 50% by weight is fired at a predetermined temperature.
According to the method disclosed in this Patent Publication, it is possible to easily form a capacitor within the alumina ceramic circuit board.
In this production method, as an amount of molybdenum powder and/or tungsten powder gradually increases, the relative dielectric constant of the resultant ceramic dielectric body also increases.
However, if the added amount of conductive substance exceeds 50% by weight, a resistance of the obtained ceramic body suddenly decreases to exhibit electrical conductivity.
Accordingly, in the method disclosed in the Patent Publication, it is possible to increase the mixed amount of a conductive substance by more than 50% by weight, whereby the relative dielectric constant of the resultant dielectric body is at most 17 or so.
On the other hand, there has been a great demand for a dielectric body having a higher dielectric constant in a circuit board of alumina ceramic or the like.
If the dielectric body having a higher dielectric constant could be formed by mixing the conductive substance in the dielectric substance, an effective means would be obtained for forming a capacitor having a high capacitance in the circuit board.